1. Field of the Invention
This invention is directed to wellbore drilling top drive systems; parts thereof; multi-seals for shafts thereof; and methods of their use.
2. Description of Related Art
The prior art discloses a variety of top drive systems; for example, and not by way of limitation, the following U.S. patents present exemplary top drive systems and components thereof: U.S. Pat. Nos. 4,458,768; 4,807,890; 4,984,641; 5,433,279; 6,276,450; 4,813,493; 6,705,405; 4,800,968; 4,878,546; 4,872,577; 4,753,300; 6,007,105; 6,536,520; 6,679,333; 6,923,254—all these patents incorporated fully herein for all purposes.
Certain typical prior art top drive drilling systems have a derrick supporting a top drive which rotates tubulars, e.g., drill pipe. The top drive is supported from a travelling block beneath a crown block. A drawworks on a rig floor raises and lowers the top drive. The top drive moves on a guide track.
The prior art reveals a variety of elastomeric lip seals for sealing against rotating shafts. Such seals are frequently used to contain lubricating oil in gear boxes and other mechanical assemblies. Because of their rubbing contact with an adjacent shaft, such seals eventually wear or are damaged to the point that the lubricant or oil they are meant to contain may leak out, causing various negative consequences. Repair or replacement of such seals can entail significant time and expense, and lost production, often requiring the removal of other machine components before clear access to the seal can be obtained.
In the prior art are a variety of top drives which have a rotating main shaft and a thrust bearing apparatus which bears the weight of the top drive and of tubulars connected thereto. In order to prevent lubricant for the thrust bearing apparatus from flowing down, a shaft seal is used with a seal member that contacts the exterior surface of the rotating shaft. When these seals wear out, it is an expensive and time-consuming task to access them and replace them.